static void GIFReadImageData(struct GIFImage *image, FILE *stream)
{
int minCodeSize;
unsigned char **rows;
unsigned int width, height, interlaced;
unsigned char *colors;
unsigned int numColors;
unsigned int xpos, ypos;
int pass, val;
GIF_TRACE(("Reading Image Data\n"));
/* Initialize the compression routines. */
GIF_FGETC(minCodeSize, stream);
if (minCodeSize >= LZW_BITS_MAX) /* this should be in fact <= 8 */
GIFError("GIF/LZW error: invalid LZW code size");
if (LZWReadByte(LZW_TRUE, minCodeSize, stream) < 0)
GIFError("Error reading GIF image");
/* Ignore the picture if it is "uninteresting". */
rows = image->Rows;
if (rows == NULL)
{
#if 0
while (LZWReadByte(LZW_FALSE, minCodeSize, stream) >= 0)
{
}
#else
/* This is faster, but possible LZW errors may go undetected. */
GIFSkipDataBlocks(stream);
#endif
return;
}
width = image->Width;
height = image->Height;
interlaced = image->InterlaceFlag;
GIFGetColorTable(&colors, &numColors, image);
xpos = ypos = 0;
pass = 0;
while ((val = LZWReadByte(LZW_FALSE, minCodeSize, stream)) >= 0)
{
if ((unsigned int)val >= numColors)
{
GIFWarning("Pixel value out of range");
val = numColors - 1;
}
rows[ypos][xpos] = (unsigned char)val;
if (++xpos == width)
{
xpos = 0;
if (interlaced)
{
switch (pass)
{
case 0:
case 1:
ypos += 8;
break;
case 2:
ypos += 4;
break;
case 3:
ypos += 2;
break;
}
if (ypos >= height)
{
switch (++pass)
{
case 1:
ypos = 4;
break;
case 2:
ypos = 2;
break;
case 3:
ypos = 1;
break;
default:
goto fini;
}
}
}
else
++ypos;
}
if (ypos >= height)
break;
}
fini:
/* Ignore the trailing garbage. */
while (LZWReadByte(LZW_FALSE, minCodeSize, stream) >= 0)
{
}
}
int /* PRIVATE */
pngx_read_gif(png_structp png_ptr, png_infop info_ptr, FILE *stream)
{
/* GIF-specific data */
struct GIFScreen screen;
struct GIFImage image;
struct GIFExtension ext;
struct GIFGraphicCtlExt graphicExt;
int code;
unsigned char *colorTable;
unsigned int numColors;
unsigned int transparent;
unsigned int numImages;
/* PNG-specific data */
png_uint_32 width, height;
png_bytepp row_pointers;
/* Set up the custom error handling. */
pngx_err_ptr = png_ptr;
GIFError = pngx_gif_error;
GIFWarning = pngx_gif_warning;
/* Read the GIF screen. */
GIFReadScreen(&screen, stream);
width = screen.Width;
height = screen.Height;
/* Set the PNG image type. */
png_set_IHDR(png_ptr, info_ptr,
width, height, 8, PNG_COLOR_TYPE_PALETTE,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
/* Allocate memory. */
row_pointers = pngx_malloc_rows(png_ptr, info_ptr, (int)screen.Background);
/* Complete the initialization of the GIF reader. */
GIFInitImage(&image, &screen, row_pointers);
GIFInitExtension(&ext, &screen, NULL, 0);
transparent = (unsigned int)(-1);
numImages = 0;
/* Iterate over the GIF file. */
for ( ; ; )
{
code = GIFReadNextBlock(&image, &ext, stream);
if (code == GIF_IMAGE) /* ',' */
{
if (image.Rows != NULL)
{
/* Complete the PNG info. */
if (image.InterlaceFlag)
pngx_set_interlace_type(png_ptr, info_ptr,
PNG_INTERLACE_ADAM7);
colorTable = GIFGetColorTable(&image, &numColors);
pngx_set_GIF_palette(png_ptr, info_ptr, colorTable, numColors);
if (transparent < 256)
pngx_set_GIF_transparent(png_ptr, info_ptr, transparent);
/* Inform the GIF routines not to read the upcoming images. */
image.Rows = NULL;
}
++numImages;
}
else if (code == GIF_EXTENSION && ext.Label == GIF_GRAPHICCTL) /* '!' */
{
GIFGetGraphicCtl(&ext, &graphicExt);
if (image.Rows != NULL && graphicExt.TransparentFlag)
if (transparent >= 256)
transparent = graphicExt.Transparent;
}
else if (code == GIF_TERMINATOR) /* ';' */
break;
}
/* Deallocate the GIF reader's extension buffer.
* Use free() in conjunction with the reader's realloc().
*/
if (ext.Buffer != NULL)
free(ext.Buffer);
/* FIXME:
* Deallocate ext.Buffer on error, to prevent memory leaks.
*/
if (image.Rows != NULL)
png_error(png_ptr, "No image in GIF file");
return numImages;
}
